An award-winning director discusses the challenges of making a documentary about a top secret digital weapon. Officials from both countries believed to be responsible for the virus meant to slow Iran's nuclear program won't publicly acknowledge it ever existed.

In his recently released film "Zero Days," award-winning documentary filmmaker Alex Gibney takes on an especially tough challenge: Making a movie about a top secret program that few people will publicly acknowledge ever existed.

Designed to slow down Iran's nuclear program, the Stuxnet computer virus is believed to be the world’s first digital weapon, developed by both the US and Israel. But even now, years after the attack on Natanz uranium enrichment plant, and long since researchers discovered the virus on computers in other countries, officials from either country won't acknowledge it – at least on camera.

"We have a montage of people in the film saying, 'We can't talk about this,' or, 'No, it's classified, can't talk,' " Mr. Gibney tells the latest edition of The Cybersecurity Podcast. "These were people ... who knew very well what was going on and had intimate knowledge of it."

"The frustrating part for me was that they simply wouldn't address it in any kind of broad sense," he continued. "It wasn't like I was asking them to give up secret codes, or betray agents in the field. It had a kind of 'Emperor's New Clothes' quality to it."

Also on this episode, cohosts Peter Singer of New America gives the inside story of what it's like to testify on Capitol Hill and Passcode deputy editor Sara Sorcher talks about the 18-year-old who hacked the Pentagon in the US government's first-ever bug bounty program.